The genetic bases of the porphyrias

Porphyria cutanea tarda: an under-recognised manifestation of haemochromatosis

We present a case of a woman who presented with a photosensitive skin rash and blisters on her extremities which did not improve with steroids. These were associated with polyarthralgia and a deranged liver function test on her admission. Further workup revealed that the patient has an undiagnosed porphyria cutanea tarda (PCT) and hereditary haemochromatosis. The patient later underwent regular venesections which improved her condition. This case report not only illustrates the challenge in diagnosing PCT but also aims to highlight the association between PCT and hereditary haemochromatosis.

Drug-Induced Protoporphyria in Beagle Dogs

As part of regulatory safety testing program, a 13-week oral toxicity study with a new antipsychotic drug candidate was performed in beagle dogs. During this study, dark red/brown feces were recorded in treated dogs and increases in liver parameters (alanine aminotransferase, alkaline phosphatase, bilirubin) were measured biochemically. At the end of the study, livers of high-dose (50 mg/kg) animals were (mottled) dark brown, sometimes with pale foci. Histopathological examination of these livers showed dark globular pigment deposits in the hepatocellular cytoplasm and within the bile canaliculi. Varying numbers of inflammatory cell infiltrates were additionally present in association with the deposits. These pigment deposits showed birefringency with characteristic “Maltese Cross”-like structures under polarized light. Electronmicroscopy revealed the typical, so-called “sunburst” pattern with radiating double-lined crystalline structures. These morphologic characteristics strongly indicated at the presence of porphyrins, which was definitely confirmed biochemically. Published reports of drug-induced hepatic porphyria in dogs are rare. The possible underlying mechanism in the dog and man is discussed.

The acute hepatic porphyrias: current status and future challenges

The porphyrias are predominantly inherited metabolic disorders, which result from a specific deficiency of one of the eight enzymes along the pathway of haem biosynthesis. Historically, they have been classified into hepatic and erythropoietic forms, based on the primary site of expression of the prevailing dysfunctional enzyme. From a clinical point of view, however, it is more convenient to subdivide them into acute and non-acute porphyrias, thereby primarily considering the potential occurrence of life-threatening acute neurovisceral attacks. Unrecognised or untreated, such an acute porphyric attack is associated with a significant mortality of up to 10%. The acute hepatic porphyrias comprise acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase deficiency porphyria. Making a precise diagnosis may be difficult because the different types of porphyrias may show overlapping clinical and biochemical characteristics. To date, the therapeutic possibilities are limited and mainly symptomatic. In this overview we report on what is currently known about pathogenesis, clinic, diagnostics, and therapy of the acute hepatic porphyrias. We further point out actual and future challenges in the management of these diseases.

An unhappy triad: Hemochromatosis, porphyria cutanea tarda and hepatocellular carcinoma-A case report

Liver fibrosis and cirrhosis are predisposing factors for the development of hepatocellular carcinoma (HCC). Hemosiderosis has also been described to trigger carcinogenesis. A significant iron overload, as found in hereditary hemochromatosis (HHC), is a risk factor for HCC and may also promote the symptoms of porphyria cutanea tarda (PCT). A 68-year old male patient presented to our clinic with a suspected HCC, elevated alpha-fetoprotein but normal liver function tests. He reported a 25 year-old history of vitiligo upon exposure to sunlight. The patient underwent an extended left hemihepatectomy, and the recovery was uneventful, with the exception of a persistent hyperbilirubinemia. Perfusion problems and extrahepatic cholestasis were ruled out by CT-scan with angiography and MR-cholangiopancreatography. However, MRI showed an iron overload. Histology confirmed the HCC (pT3, pN0, G3, R0) and revealed a portal fibrosis and hemosiderosis. Based on the skin lesions we suspected a PCT that was confirmed by laboratory tests showing elevated porphyrin, uroporphyrin, coproporphyrin and porphobilinogen. Concurrently, molecular diagnostics revealed homozygosity for the C282Y mutation within the hemochromatosis HFE gene. After phlebotomy and normalization of liver function tests the patient was discharged. This is the first case ever showing the unusual combination of HCC in a fibrotic liver with HHC and PCT. This diagnosis not only warrants oncological follow-up but also symptomatic therapy to normalize iron metabolism and thereby improve liver function and alleviate the symptoms of HHC and PCT. Thus progression of fibrosis may be prevented and liver regeneration supported.

[Laboratory tests and therapeutic strategies for the porphyrias]

The porphyrias are a heterogeneous group of predominantly hereditary metabolic diseases resulting from a dysfunction of heme biosynthesis. Most of the porphyrias can manifest with a broad range of cutaneous symptoms on the sun-exposed areas of the body, whereas other variants reveal life-threatening acute neurological attacks. Further, mixed types of porphyrias exist. Besides the skin, other organs can be affected, such as the liver and the central nervous system. Therefore, interdisciplinary supervision of these patients is mandatory. In this review we will first present the clinical picture and diagnosis of the porphyrias, including the specific biochemical laboratory tests and a diagnostic algorithm. Thereafter, the current therapeutic concepts will be briefly addressed. Finally, we introduce the European Porphyria Initiative (EPI), an association of various European porphyria centers that is aiming at gathering the broad experience of internationally renowned porphyria experts for the development of European consensus guidelines for diagnosis and treatment of these metabolic disorders.

Hereditäre Photodermatosen

Hereditary photodermatoses are characterized by an increased photosensitivity caused by an inherited single gene defect. With few exceptions, they manifest in early childhood, reveal heterogeneous clinical symptoms, and are difficult to treat. Although these diseases are rare, it is very important to make an accurate diagnosis on the basis of clinical symptoms, specific diagnostic tests, and direct DNA analysis. We review the spectrum of inherited photodermatoses, including porphyria cutanea tarda, erythropoietic protoporphyria, actinic prurigo, Kindler syndrome, and disorders associated with a defect in DNA repair, including xeroderma pigmentosum, trichothiodystrophy, Cockayne syndrome, and Bloom syndrome. Early diagnosis may prevent complications associated with prolonged unprotected exposure to sunlight and makes it possible to offer genetic counseling and, when indicated, prenatal diagnosis to families at risk for these rare heritable disorders.

Dual porphyrias revisited

The porphyrias are clinically and genetically heterogeneous metabolic diseases, which predominantly result from a hereditary dysfunction in the pathway of haeme biosynthesis. Currently, at least eight different forms of porphyrias can be differentiated, all of them characterized by a specific enzyme deficiency that is either inherited in an autosomal-dominant fashion, autosomal recessively or, in the case of porphyria cutanea tarda, might also be acquired. All genes encoding these enzymes have been cloned and several mutations underlying the different types of porphyrias have been reported. Traditionally, the diagnosis of porphyria is made on the basis of clinical symptoms, characteristic biochemical findings and enzyme assays. In some porphyria patients and families, however, these diagnostic tools can reveal simultaneous findings compatible with two different forms of porphyria, a phenomenon referred to as dual porphyria. Here, we give an overview on what is currently known about these peculiar variants of porphyria and suggest that, whenever feasible, molecular genetic analysis should complement the analytical techniques used to characterize patients and families in which a double enzymatic deficiency within the haeme biosynthetic pathway is assumed.

Kortikale Amaurosis und Status epilepticus bei akuter Porphyrie

The most common neurologic manifestations of acute intermittent porphyria (AIP) are autonomic visceral neuropathy, peripheral motor neuropathy, and CNS dysfunctions including seizures and neuropsychiatric disturbances. In rare instances, however, AIP patients have presented with acute cortical blindness. We present a 20-year-old woman who suffered her first attack of AIP. Following 1 week of abdominal pain, she was transferred from a surgical department because of sudden visual loss and deterioration of consciousness. On admission, she developed several generalized seizures. Magnetic resonance imaging showed bilateral DWI lesions occipitally and in the left anterior circulation. Cerebrospinal fluid, MR angiography, and duplex ultrasound were normal. On the following day, sedation and intubation became necessary because of a generalized status epilepticus. Analysis of porphyrinogens in blood, urine and stool showed significantly elevated values. Intravenous therapy with häm-arginate was initiated and antiepileptic therapy was changed to gagabentine. Under this therapeutical regime she remained stable and extubation was possible 48 h later.

The molecular basis of porphyria cutanea tarda in Chile: Identification and functional characterization of mutations in the uroporphyrinogen decarboxylase gene

The porphyrias are heterogeneous disorders arising from predominantly inherited catalytic deficiencies of specific enzymes in heme biosynthesis. Porphyria cutanea tarda (PCT) results from a decreased activity of uroporphyrinogen decarboxylase, the fifth enzyme in heme biosynthesis. The disorder represents the only porphyria that is not exclusively inherited monogenetically. In PCT, at least two different types can be distinguished: acquired/sporadic (type I) PCT, in which the enzymatic deficiency is limited to the liver and inherited/familial (type II) PCT, which is inherited as an autosomal dominant trait with a decrease of enzymatic activity in all tissues. In an effort to characterize the molecular basis of PCT in Chile, we identified eight mutations in 18 previously unclassified PCT families by polymerase chain reaction, heteroduplex analysis, and automated sequencing. To study the role of these mutations in disease causality, in vitro expression of all novel missense mutations was studied. Our results indicate that the frequency of familial PCT in Chile is approximately 50%, thus, to our knowledge, representing the highest incidence of familial PCT reported to date. The data further emphasize the molecular heterogeneity in type II PCT and demonstrate the advantages of molecular genetic techniques as a diagnostic tool and in the detection of clinically asymptomatic mutation carriers.

Diagnosis and treatment of the acute porphyrias: an interdisciplinary challenge

The porphyrias comprise a group of fascinating disorders resulting from predominantly inherited as well as acquired deficiencies of one of the eight enzymes along the pathway of heme biosynthesis. On the basis of clinical aspects, the different types of porphyrias can be classified in acute and non-acute forms. However, an exact classification is often difficult since the porphyrias might reveal unspecific clinical symptoms and/or overlapping biochemical features. In particular, this is true for the acute porphyrias which can present with life-threatening acute neurovisceral attacks that require immediate medical intervention. Due to the multiple facets of these disorders, the diagnosis and treatment of the acute porphyrias should always imply a close interdisciplinary collaboration to serve patients and their families most effectively.